Ceramic materials of the formula RCrO.sub.3, where R is a rare earth oxide as yttrium oxide are known in the art. See, e.g., U.S. Pat. No. 3,475,352. These materials, although useful in electroconductive applications such as electrodes, suffer from low chemical stability when exposed to high temperatures above 1600.degree. C., low resistance to thermal cycling at temperatures above 1500.degree. C., and the inability to be heated at high heating rates. These deficiencies have limited the use of these materials in applications where property stability is important.
A need therefore exists for rare earth oxide ceramic materials that have improved stability and which are useful in electroconductive applications as well as in high temperature environments. Such applications include the drying or sterilization of various articles.
One known method of sterilization uses infrared radiation (IR). For example, U.S. Pat. No. 4,774,415 discloses a device for sterilizing a hose coupling from a dialysis apparatus. One drawback of this device is that the source can cause insufficient sterilization of portions of the articles which do not receive the appropriate exposure of IR. If the time of sterilization is increased to compensate for the inadequate exposure, portions of the articles to be sterilized can be overheated. When articles made of metals and glass are overexposed, they can either be melted due to overheating or discolored due to oxide film formation.
Automatic regulation of the temperature by using a temperature detector and electronics for control and operation does not improve this problem because the articles often have different sizes and masses which are in conflict or incompatible with the constant and inflexible size and mass of the temperature detector. Thus, the present invention proposes to eliminate the above drawbacks and to increase the efficiency of sterilization by decreasing the sterilization time through the use of such new ceramic materials.
The drying of food products using IR produced by the use of a transforming member or screen made of mullite is known from an article by G. A. Slack entitled "Advanced Materials for Optical Windows" GE Res. Rept. No. 79CRD071, June, 1979. The primary deficiency of this method is its low drying efficiency. Thus, the present invention also proposes to increase the efficiency of IR drying methods, again through the proper selection and use of the new ceramic materials disclosed herein.